Integration of a Terrestrial Laser Scanner with Gps/imu Orientation Sensors

Direct orientation of laser systems has been widely used for airborne laser sensors but not with the terrestrial laser systems. The usual way to operate a terrestrial laser is by scanning a scene while the sensor remains static. In order to cover the whole scene, different scans can be combined by matching several common points, finally the orientation of the scene is performed by identifying and providing coordinates for a minimum of 3 points. This procedure is very time consuming leading to a very low productivity. In order to increase productivity the Institut Cartografic de Catalunya (ICC) has integrated a terrestrial laser scanner in a mobile vehicle with the aim to operating the laser while the vehicle is moving. This paper describes the integration of a terrestrial laser scanner with the GPS/IMU orientation sensors of a Land Based Mobile Mapping System. The laser pulses are synchronized to the GPS time by using a modified PPS signal from a GPS receiver. In order to transfer the reference frame from the GPS/IMU sensors to the laser sensor a number of calibration scans and control points are used and the offset and misalignment between the laser and GPS/IMU sensors is determined. The results of the calibration procedures, as well as accuracies and performance obtained by the integrated GPS/IMU/terrestrial laser system are presented in the paper.